The invention relates to barrier structures comprising nanopores. More particularly, the invention relates to structures having electroactive nanopores. Even more particularly, the invention relates to electrochemical sensors having such structures.
The detection and identification of single molecules has received increasing interest over the last few years, as there has been a realization that this can be done by analyzing transport and electrochemical phenomena through pores having nanoscale dimensions. Measurements of the ionic current through a single-protein channel incorporated into a freestanding lipid bilayer membrane can form the basis of a new and versatile method for single-molecule chemical and biological sensing, called stochastic sensing. These sensors consist of a protein pore embedded in an insulating membrane and operate by measuring the characteristic current through the pore in the presence of molecules of interest. The magnitude, duration, and rates of occurrence of the current blockage allow rapid discrimination between similar molecular species.
The main limitation in this nascent field is that the bulk of the work has been focused on biologically-based stochastic sensors using protein pores embedded in lipid bilayer membranes. The lipid bilayer membrane into which the channel is immobilized is fragile and unstable; such membranes have lifetimes on the order of a few hours and, very rarely, exceed one day. These membranes are extremely delicate and susceptible to breakage, requiring vibration isolation tables, low acoustic noise environments, and special solution handling. This is unacceptable for field-usable devices and applications outside the laboratory. Furthermore, although a range of membrane proteins, which can be modified as desired through biochemistry or mutagenesis, may be exploited as sensors, the availability of biological pores is still limited with respect to having complete freedom in pore size, structure, and composition. Attempts to fabricate solid-state nanopores that are able to mimic the ion transport properties of protein ion channels lack reproducible dimensional control at the nanometer scale.
Existing biologically-based stochastic membrane sensors are not sufficiently robust for widespread use outside a controlled laboratory setting. Therefore, what is needed is a stochastic membrane sensor that is sufficiently robust to withstand use in applications under normal conditions. What is also needed is a membrane for a stochastic sensor that is not biologically-based. What is further needed is a membrane for a stochastic sensor having a diameter that is reproducibly controllable.